This invention relates generally to slide fasteners, and in particular to a slide fastener having emergency opening means such that the fastener is normally opened or closed by a slider moving along interlockable rows of fastener elements or scoops but, in an emergency, can be forced open from its midpoint without manipulating the slider. The slide fastener of this character finds the most advantageous use on entrances of camping tents and like closure openings of other articles.
The slide fastener of the type under consideration, as heretofore constructed, typically comprises an emergency opening zone disposed in a suitable position intermediate both ends of interengageable rows of fastener elements, and top and bottom stop assemblies to limit the movement of a slider along the fastener elements. When the fastener is forced open from the emergency opening zone in an emergency such as a fire or earthquake, the slider is located in its fully closed position on the rows of fastener elements, where the slider is in contact with the top stop assembly. If this slider could be smoothly pulled down to the bottom stop assembly along the rows of fastener elements, the slide fastener would be reusable because then it can be opened and closed by the slider in the usual manner.
In reality, however, the rows of fastener elements are thoroughly disengaged from each other after the slide fastener has been forced open in an emergency, so that the slider can hardly be pulled down therealong to its lowermost position. If the slider is somehow managed to move down along the disengaged rows of fastener elements, its movement will be completely blocked as it approaches the bottom stop assembly, since then the element row portions lying between the slider and bottom stop assembly will bulge so as to form an elliptical spacing therebetween.
As the slider cannot be pulled down to its endmost position after the emergency opening of the fastener, it is impossible to open and close the fastener throughout its length. The forced downward movement of the slider is also easy to cause irregularities in the pitch of the fastener elements or the dislodgement of the elements. For these reasons the slide fastener that has been forced open in an emergency has heretofore been considered not restorable to its normal use.